Noninvasive quantification of energy transfer during mechanical ventilation

Area of Science:

• Mechanical Ventilation
• Respiratory Mechanics
• Biomedical Engineering

Background:

• Ventilator-to-patient energy transfer (ETv) contributes to ventilator-induced lung injury.
• Existing ETv formulations overlook patient respiratory muscle effort (Pmus).

Purpose of the Study:

• Develop and validate mathematical expressions for breath-by-breath ETv.
• Incorporate patient respiratory effort (Pmus) into ETv calculations.
• Utilize only airway pressure (Paw) and flow (Faw) signals for noninvasive quantification.

Main Methods:

• Derived equations from a single-compartment respiratory system model.
• Related Pmus pressure-time product (PmusPTP) to ETv in VCV and PCV modes.
• Validated models using high-fidelity Paw and Faw recordings from ventilated patients.

Main Results:

• Excellent agreement between calculated and measured ETv in both VCV (R² = 0.99) and PCV (R² = 0.98) modes.
• Low bias observed in both ventilation modes (VCV: 0.3 ± 0.9 J·min⁻¹; PCV: -0.10 ± 1.94 J·min⁻¹).
• Demonstrated accurate, noninvasive, breath-by-breath ETv quantification using only airway signals.

Conclusions:

• Developed model accurately quantifies ETv during controlled mechanical ventilation.
• Enables real-time assessment of insufflation energy dynamics.
• Provides a physiological basis for reducing ventilator-induced lung injury.